Process of distilling tar



s. P. MILLER 1,912,294

PROCESS' oF DISTILLING TAH Filed oct. 15, 1927 4 sheets-sheet 1 May 30, 1933.

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May 30, 1933 s. P. MILLER 1,912,294

PROCESS 0F DISTILLING TAR Filed Oct. l5, 1927 4 Sheets-Sheet 2 n' INVENTOR 7 BY M f4" ATTORNEYS May 30, 1933. s. P. MILLER 1,912,294

PRocEss 0F DISTILLING TAH Filed Oct. 15, 1927 4 Sheets-Sheet 3 /MB-Mfw ATTORNEYS May 30, 1933- s. P. MILLER 1,912,294

PROCESS oF DISTI'LLING lTAH Filed oct. 15, 1927 4 sheets-sheet 4 ,ZJ YIIN wm INVENTOR WM M BY jaw- 60M ATTOINEYS Patented May 30, 1933 NEW JERSEY, ASSIGNOB TO THE .AV CORPORATION F NEW JERSEY I PROCESS DISTILLING TAR .Application led October 15, 1927. Serial No. 226,324.

This invention relates to the distillation of tar, and particularly to the utilization of the heat available in the ogases roduced in-coalcarbonization plants to distill tar. and to produce oils and, pitches by such distillation. The invention will be described especially `with reference to its application to coke ovens. Y

' In the ordinary operation of by-product m coke ovens the gases produced by the coking operation pass from the individual ovens through uptake pipes and goose necks to a collector main common to the ovens ofthe battery- The gases, commonly known las foul gases, leave the ovens at high temperature, e( g., 600 to 700 C. or higher, and carry a considerable proportion of volatilized tars and oils. Ordinarily the gases are cooled as rapidly as possible by the application of sprays of ammonia liquor orammonia liquor' and tar in the goose-necks and collector main, `the heat in the gases being thereby dissipated and lost. The rapid cooling causes separation of tar vcontaining heavier oils in the collector main. Further cooling is effected vin the cross-over main which connects the collector main ,to the condensing system and an additional quantity of tar or terry oil carrying both heavier and lighter oils is thus separated. The collected tar is commonly shipped from .the

coke-oven plant toA a tar-distillation plant for distillation and separation of the oils and the production of pitches of varying qualities. vHandling losses, freight charges and distillation costs, including fuel and capital and maintenancey expenses for the vspeciall equipment required vfor distillation, add to fl@ the cost or production of the tar-distillation products.

lt is an object of. the present invention to v provide a method and .apparatus which per- V mit the distillation of tar at a coalfdistillais tion plant, such as' a coke-oven plant, the utilization oi the heat or the coal distillation gases nier that purpose, and particularly the enrichment ofthe gases in oil vapors and 'the production or clean oils directly by such distillation, together with pitches having the improvements in' various moreover, a benecial eil'ect upon the electriqualities and characteristics required byI the trade.

A further object of the invention is the utilization of the hot coal distillation gases to distill' the tar in successive operations folf 65 lowed by electrical precipitation of the gases so utilized. This permits the production of: heavier pitches and the recovery of ydistinct oil condensates, th t is to say,.a light oil from the first distillation and heavier oils 60 from the successive distillations. Several desirable products are obtained thus infa single and continuous distillation of the` tar by utilizing the hot gases as theyare discharged rom the ovens ofthe battery.

According to-the present invention the heat'of the cokefoven or other coal distillation gases as they come from the coke ovens or retorts is utilized to distill tar and to separate volatile oils therefrom by spraying or otherwise bringing the tar into intimate contact with the hot gases, and the resulting gases carrying the vapors and the Qparticles of tar and tar fog are subjected immediately to electrical precipitation to remove 'I5 the liquid and solid constituents from the gases, leaving therein the vaporsof condensible 011s which, upon A'subsequent cooling of the gases, yield 4clean oils. l p

To eii'ect the ydesired distillation the tar 80 or other material to be distilled is brought into intimate contact with the gases at the bottom of the electrical precipitator so that the line particles of tar are subjected immediately to the distilling eilt'ect of the hot gases and the resulting gases are then immediately passed through the electrical' precipitator. The gases are somewhat cooled by theabsorption of heat both as' sensible heat and as latent heat `of vaporization of the tar or other material. The distillation and separation of the vaporizable oils is thus accomplished inmediately. `The operation has,

cal precipitator operation inasmuch as the gases passing therethrough are loaded with nely divided particles oi tar or tar fog which, being separated upon the walls' of the precipitator tubes, flow downwardly and flush the tube walls tending thereby to prevent any accumulation of tar or pitch, thereby maintaining the precipitator in a condition for continuous operation. The tar and pitch particles which are agglomerated in the electrical precipitator and which flow backwardly into the lower part thereof are again subjected to heating by the hot gases and to further distillation effect thereby. The liquid thus subjected to the repeated Yheating effect of the gases with resultant loss of volatile constituents collects in the bottom of the electrical precipitator in the form of pitch and may be withdrawn and utilized as such while the gases, which escape from the top of the precipitator after being freed from solid and liquid particles, may be cooled to condense and recover clean oils therefrom.

A It will be undestood by those skilled in the art that the coke oven gases arising from the ovens contain vapors of condensable coal tar oils and contain also, as entrained material, coal and coke dust and non-volatile pitch or tarry constituents commonly known as tar fog. At high gas temperatures, the tar fog is present as high melting point pitch. At lower temperatures, the melting point of this pitch is lower, due to condensation from the gases of heavier oils which blend with the pitch and lower its melting point. At teme peratures applying in the ordinary collector main and in cross-over mains and condensers, such lar e quantities of oils have been condensed tat the tar fog is present as ordinary tar.

It will be understood. therefore, that the pitch finally resulting `from the .process of my invention is made up partly of the residue of distillation of the tar added and partly of the pitch normally occurring in the hot coke oven gases.

Likewise, the clean oils recovered from the gases cleaned by the electrical precipitator are made up partly of oils resulting from distillation of the added tar and partly of the oils normally occurring as vapors in the hot coke oven gases.

The dew points of the gases for the several constituents carried therein as vapor are lower than the normal boiling points of these constituents and by suitable regulation of the temperature of the gases during distillation, for example, by variation of the rate at which tar is introduced, it is possible to retain the desiredoils therein as vapors while the heavy tarry constituents are precipitated. rlhus, by controlling the temperature of the gases either before or during the distillation all or. substantially all of `(the tarry constituents of the tar to be distilled ein be retained in the liquid phase while the desired oils are vaporizedand carried away with-the gases. The temperature of the exit gases should, to accomplish the intended pur pose, be maintained above the dew point of the gases for the most readily condensable oil constituents desired so that substantially all of the desired oils will be retained in the gases as vapors while the tarry or pitch constituents remain as liquid, part of which settles out of the gas and part of which is separated from the gases in the electrical precipitator and is blended with the pitch at the bottom of the precipitator.

T he cooling of the gases, when the gases are to be employed below their maximum temperature, can be elected not only by modifying the amount of tar introduced to the stream of gases but also by employing other cooling agents such as oil vor ammonia liquor, either or both'of which maybe sprayed with the tar into the bottom of the electrical precipitator or introduced to the gases before they enter the precipitator. Or the oil or ammonia liquor or other aqueous cooling agent can be mixed with the tar beforethe latter is brought intimately in contact with the hot gases. By thus cooling the gases to the desired degree the temperature of distillation and of subsequent separation of the tar and pitchnconstituents from the gases can be regulated and controlled to ensure the production of pitches having the desired consistency andthe recovery of the required proportion of oils of desired composition from the tar; while by avoiding such cooling,'and by employing the gases at a high temperature, effective distillation can be obtained with a smaller amount of gases, and high melting point pitches and high oil yields readily obtained.

The heat available in the gases from a.

coke-oven battery` is from twenty-tive to forty times the amount required for the distillation of all of the tar produced by the battery to soft or medium pitch. Consequently if all of the heat available in the hot gases is utilized it will be necessary either to add water or ammonia liquor in regulated amounts to the gases or to supply tar or oil from other sources; as an alternative the tar from the battery can be accumulated and distilled at intervals by the operation as described. lf only tar from a single battery is to be distilled it will be suiiicient usually to provide one or more precipitators which may be supplied with hot gases from one or more of the ovens of the battery.

rlhe invention presents the advantage,

among others, that it enables the hot coke -oven or other coal .distillation gases to be employed fordistillation at a temperature approaching their maximum temperature, thus enabling rapid distillation to be obtained, high melting point pitches to be readily produced, and large increase in vapors, particularly vapors of heavy or high boiling oils to be obtained in the escaping gases.

In, carrying out the invention no substantial modification of the usual coke-oven battery and recovery system is required, that is to say, the ovens may be connected through the usual uptake pipes and goose-necks to the ordinary collector main wherein the gases are cooled by spraying with ammonia liquor or ammonia liquor and tar to reduce the temperature of the gases and to separate tar constituents therefrom. The gases may be conveyed thereafter through the usual 'crossover main to condensers in which further cooling is eliected to separate tarry oils from the gases which may be treated thereafter in the usual manner for the recovery of light oils and ammonia. The tar and tarry oils which are separated in the manner described may be subjected to distillation in accordance with' the present invention.

AFor the purpose of distilling the tar and oils one or more of the ovens of the battery may be connected to the electrical precipitator either through the usual uptake pipes or through separate uptake pipes provided for that purpose. lf the usual uptake pipes supply the hot gases to the electrical precipitator, valved connections can be provided so that the gases may be diverted to the collector main when distillation is not carried out. Preferably` the electrical precipitator is disposed at the rear of the ovens and is connected to one or more of the ovens through a separate uptake pipe or pipes l while the ovens are also connected to the ordilector main connected to it, may be insulated advantageously to prevent the loss of heat from the gases. This is particularly desirable if the recovery of the maximum quantity of heavy .oils from the gases subsequent to cleaning thereof is desired.

The operation of an electrical precipitator consists in passing the gas to be treated between electrodes whose difference in electrical potential isvery great. Experience has shown that it is best to use a high potential rectified alternatin current. The alternating current (the primary) is sent through a stepup transformer to produce the high potent-iai current (the secondary) which is then rectified to an intermittent uni-directional current, for example, by means of a rotary converter. The rectified current is delivered from the`eonverter to the electrical precipi ator at practically the potential at .which it leaves the transformer.

The electrical precipitator consists essentially of a group of vertical pipes with a wire or rod in the centre of each, thepipes being connected to proper headers for the intro duction and discharge of the gases. The pipes generally constitute the positive electrodes and the wires or rods the negative electrodes. The size of the'pipes may vary, but in general pipes of less than six inches in diameter are not employed. Electrical precipitators with pipes siX inches in diameter using secondary voltages from 35,00() to 50,000 volts are'satisfactory for the purpose of this invention. It is generally best to operate with maximum potential difference (secondary current) between electrodes, this maximum being just below the break-down voltage at which arcing occurs. It will be understood that the wires or rods are insulated from the tubes and casing.

The etliciency of the cleaning is dependent upon several variables. Satisfactory cleaning of the gas may be accomplished if the time of treatment is of the order of one second, although this time may be varied widely, depending upon the character' of the oil to be removed from the gases after passing through the precipitator. In Working with tubes six inches in diameter and nine feet long, for example, an oil substantially free from all terry matter or free carbon has been obtained with a time of treatment of from one and onehalf to two seconds, that is, a gas velocity through the tubes of from 6 to 4.5 feet per second. This gives an efiiciency of cleaning of approximately ninety-nine per cent. Il small amounts of tar are not objectionable in the oils recovered, the time of treatment may be limited, e. g. to 0.5 to one second, or a gas velocity of eighteen to nine feet per second may be employed, to obtain incomplete cleaning of the gases.

The'electrical precipitator is provided with a chamber below the tubes which is separated therefrom-preferably by a baille. The hot gases from .the uptakel pipe or pipes are delivered directly to this chamber and pass therethrough in intimate contact with the tar or oil to be distilled which is introduced to the chamber, e. g. through a plurality of spray nozzles under suiilcient pressure to cnsure the sub-division of the tar or oil into fine particles which facilitate the distillation of the oil constituents. As hereinbefore indicated, oil or an aqueous cooling agent such as ammonia liquor can be introduced either with the tar or through separate spray nozzles or these cooling media can be delivered to the goose-necks and mingled with the hot gases before they enter the chamberat the bottom of the precipitator, where the gas tcmperature is too high or; the tar supply is insuliicient to utilize all the heat of the gases at a high temperature. By regulation of the amount of the cooling media supplied, the temperature of the gases can be regulated at will and the distillation can be conducted, therefore, in a manner to permit the production of pitches and oils having the desired characteristics.

As a substitute'for or adjunct' to the spray nozzles through which the tar or oil to be distilled is introduced, the chamber at the bottom of the precipitator may contain means for mechanically atomizing or spraying the tar or pitch intovthc gases, such as a cylinder which is adapted to be rotated at relatively high speed. This cylinder may dip slightly into a body of tar or oil in thebottom of the chamber and may thus throw the tar or oil in the form of relatively small particles into the stream of gases flowing through the chamber to facilitate intimate contact between the tar or oil and the gases. The tar or oil is thus thrown repeatedly into the stream of gases and is subjected to the heat thereof for the purpose of distilling the volatile constituents, leaving pitch which may be Withdrawn either continuously or intermittently as a product of the distillation. Other devices for causing intimate contact between the tar or pitch and the gases may be used.

The gases escaping-from the electrical precipitator maybe delivered to a suitable condensing system in which they may be cooled in order to separate the desired conlensable oils. These oils, which consist of a mixture of several constituents, may be recovered by total condensation in a single fraction, or they may be fractionally condensed. The dew points :of the gases for these several constituents are different and it is possible by fractional condensation to recover' oils having varying characteristics, such as a. heavy creosote oil and a lighter tar acid or carbolic oil.A Fractional condensation may be carried out in condensers designed to cool the gases in stages and to separat-e the condensed oils in fractions therefrom. Aft-er such separation of the oil constituents the remaining gases may be delivered to the ordinary collector or crossover mainin which ease they mingle with the gases from the other ovens of the battery. or they may be conveyed to the eX- hauster which maintains the pressure balance in the gas systemV and there mingle. with the gases from the other ovens of the battery after the latter have been cooled to condense and remove tar and oil therefrom.

The invention can he utilized also hy subjecting the tar to be distilled to distillation in successive steps with hot gases from the ovens followed hy electrical precipitation of the gases. The gases from any desired number ot' ovens may he utilized in this manner. lret'erably one. two or more ovens are connected to cach successive distillation apparatus. The gases to he thus utilized can he diverted from the ordinary uptake pipes by the provision of suitable connections and valves, but preferably separate uptake pipes are provided, for example, at the rearof the ovens and these uptake pipes are connected to the distillation apparatus, valves being provided to permit diversion of the gases from the selected ovens from the usual collector main into the distillation apparatus. The distillation apparatus may vary in form. A suitable apparatus consists of a short collectormain divided by diaphragms into separate distilling sections, each of which may be connected to one or more ovens. An electrical precipitator may be mounted above each of the distilling sections of the collector main and may be connecteddirectly thereto so that the gases after intimate contact with the tar to be distilled pass immediately through the electrical precipitators for the purpose of separating entrained liquid and solid particles from the gases. The clean gases may then be conveyed separately to condensing systems wherein they are cooled to recover the condensable constituents. The diaphragms should extend from the top of the collector main toward 'the bottom thereof to the extent required to prevent mingling of the gases from the separate sections, that is to say, a seal should be provided by the tar and pitch flowing through the collector main at .the bottom thereof. The tar and pitch may thus fiow through the main, being subjected therein to successive distillation by the hot gases in the distillation sections of the main. The progressive distillation of the tar and pitch results inthe separation of lighter and. heavier oil constituents progressively and the production of a pitch having the desired characteristics which may be withdrawn from the end of the short collector main. The degree of hardness of the pitch thus produced can be modified by regulating the conditions of distillation. Pitch of intermediate melting point may of course be withdrawn from intermediate compartments.

The tar and pitch to be distilledmay be introduced at one end of the collector main and may be intimately mingled with the hot gases, for example, by means of spray nozzles which divide the tar or pitch into relatively fine particles, or by means of mechanical spraying or aton'i'izing devices. If spray nozzles are employed, the tar or pitch in the separate distillation sections can be withdrawn and recirculated through thespray nozzles by providing pumps and suitable connect ions for that purpose. Preferably, however. the mingling of the tar with thc hot gases is effected by the provision in the separate sections of mechanical atomizers, e. g., evlinders rotated at high speed and adapted lo dip into the bodies of tar and pitch in thc bottom ot' each section and to throw the tar or pitch in the form of line particles into the hot gases introduced to the respectivesections. Ihus, the tar' or pitch in'each section is subjected repeatedly to intimate contact with the hot gases to eect the further .5 distillation of the tai* or pitch. The distillation is also-improved by contact of the hot gases with the liquid ,constituents which are returned constantly from each of the electrical precipitators as the result of the separation of such constituents from the gases therein. @ther forms of .agitating devices adapted to accomplish the purpose of the invention may be used -in place of or as adjuncts to either the spray nozzles or the rotating cylinders.

The electrical precipitators may be of the type hereinbefore described. A number of such precipitators may be used andthe number of sections'in the short collector main may be similarly multiplied so as to provide for any number of successive distillations of the tar and pitch by contact with the hot gases from the ovens. Each distillation section of the collector main may be connected to any number of ovens to secure the necessary supply of hot gases for distillation of the tar and pitch. ln place of .the-short collector main divided by diaphragme into separate distillation sections, independent receptacles can be utilized and the tar and pitch can be directed in succession into such receptacles, it being understood` that each receptacle will be connected to ari-electrical precipitator and that provision will be made for the intimate contact of the tar and pitch to be distilled 'with the requisite amount of hot gases, either by the use of spray nozzles withv means for recirculating the tar or pitch therethrough or.`

by the provision of suitable mechanical agb tating devices in each receptacle.

The gases, after cleaning in the electrical precipitators, may be cooled and the oil vapors condensed in a single condenser, but preferably separate condensers will be providedY to permit the recovery of the lighter and heavier oil constituents which are removed from Athe tar and pitch by the suocessive distillations. After condensation of the condensable constituents the gases can be delivered either to the ordinary collector or cross-over main Where they mingle with the gases from the remaining ovens ofthe batter i or they can be delivered to and mingled wit i the gases from the remaining ovens after the latter have passed through the ordinary. con

densing system The tar or oil which is distilled according to the present invention may be tar or oil produced at the. same coke-oven plant or at @o another plant. .The tar may be a heavy tar,

light tar or heavy or light tar constituents which it is desired to distill for the purpose of separating distillate oils therefrom. 'Tar from other sources, such as gas-house tar,

@5 vertical retort tar, or water-gas tar, etc., may

also be distilled. Where blended or com posite pitches are desired or composite or blended distillates, two or more dillerent kinds of tar can be mixed in suitable proportions and distilled together, giving di-l rectly a composite pitch product. For example, horizontal gas-retort tar with high free .carbon content can be admixed with coke-oven tar and the mixture can be disrtilled to give ai composite pitch higher in free carbon than the pitch from the coke-oven tar alone and to give a composite oil distillate. The invention may be utilized like- Wise to distill oils and particularly dirty or contaminated oils for the purpose of recovering clean oils and pitch residues therefrom. Such oils' can also be utilized for the purpose of regulating the 'temperature of distillation in the manner hereinbefore described.

The present invention is of more or less general application to the distillation of tar and oils and the recovery of distillates. The invention involves utilization of the hot Fcoke-oven gases for the distillation of tar or showing apparatus embodying the invention and adapted furthe 4practice thereof. In the drawings,

Fig. 1 is a plan view of a portion of the coke oven illustrating the application of the invention thereto;

Fig. 2 is a vertical section through the electrical precipitator;

Iig. 2A is another section through the precipitator; f

Figs. 3 and 3A are similar views illustrating the application of the rotating cylinder therein;

Fig. 4 -is a plan view of a portion of a cokeoven battery illustrating the application of supessive distillation of the tar and pitch; an

Fig. 5 is un enlarged vertical section of a short collector main having separate distilu lation sections with electrical precipitators connected thereto.

Referring to the drawings, 5 indicates a battery of coke ovens having individual up take-.ipipes and goose-necks 6 which connect the ovens with a collector main 7.- The latter maybe of any usual form and construction and is designed to receive all of the .gases lfrom the individual coke ovens and to deliver thein through a. centre box 8 to a crossover main 9 which is connected to the condensing apparatusy hereinafter described. The collector main may be providedwith a plurality of spray nozzles 10 designed to distribute ammonia liquor or ammonia liquor and tar to the gases flowing through the collector main for the purpose of reducing the temperature of these ;ases'and of flushing the collector main. The ammonia liquor may be delivered to the spray nozzles through pipes 11 and 12 connected thereto and to a source of supply such as a tank 13, a pump 14 being provided to permit the introduction of the ammonia liquor or ammonia liquor and tar to the collector main under a suitable pressure. uid may be supplied likewise to the goosenecks leading to the collector main through spray nozzles 15 which are supplied by the pipe l2.

he cross-over main 9 conveys the partially cooled gases to condensers 16 wherein they are further cooled to separate tarry oils therefrom. The tar and oils vwhich separate in the cross-over main and in the condensers may be withdrawn through pipes 17 and 18 and delivered to decanters 19 and 20 wherein the ammonia liquor is rseparated from the tar and "tarry oils. The' tar and tarry oils may be delivered through pipes 21 to a stora e receptacle 22 to be Withdrawn as hereina ter described and subjected to the heating effect of hot coke-oven gasesy for the purpose of distilling the tar and tarry oil. Tar from 19 and tarry oils from 20 may if desired be kept separate by providing storage 22. The gases from the condensers 16 are drawn through an exhauster 23 and are delivered thence to the usual apparatus for the recovery of ammonia and light oils, etc. The apparatus as hereinbefore described is that commonly employed in by-product recovery systems in connection with coke ovens, and it will be understood that such apparatus may be operated in the usual manner for the pur ose of cooling and condensing the tar and) tarry oil constituents of the gases. The application of the present invention does not, therefore, involve any considerable modification of the ordinary cokeoven plant. In carrying out the invention the electrical precipitator or precipitators employed for distillation of the tar may be disposed conveniently at the rear of the ovens. .Each precipitator may be connected to a single oven or to a plurality of ovens. Valves may be provided to divert the hot coke-oven gases from the selected ovens into the precipitators, the connections between these ovens and the ordinary collector main being at the same time closed.

Each precipitator may consist of a shell 24 enclosing a number of tubes 25 supported in heads 26 and 27 within the shell. A cham- The cooling liqber 28 isfprovided at the lower end of the an uptake pipe and goose-neck 30, forexample.- An outlet 31 permits the escape of the gases from the precipitator after the latter have p'assed through the tubes.

A plurality of electrodes 32 preferably in `the form of metal rods extend through the tubes and are supported from a bus-bar 33 located near the upper end of the tubes. The bus-bar 33 extends at both ends into casings 34 which. enclose insulators 35 upon which the busbar is supported. The high tension current line extends into one of thecasings and connects with the bus-bar, thus supplyingl the necessary current from any suitable source of uni-directional current under highl tension.` The casing of the separator j; isgrounded lor otherwise 'connected' 'tof'tli'eA source of current to complete the circuit. The casing and tubes form the positive electrode, the electrodes connected to the bus-bar being negative. The form and arrangement of the conductors in the circuit can be Varied. The arrangement should be such as to supply high tension uni-directional current to the electrodes, thereby permitting continuous silent discharge between the electrodes and the tubes through which the gases pass.

The tar oroil to be distilled is introduced to the chamber at the bottom of the precipitator through a plurality of spray nozzles 36 which are supplied through a pipe 37 and pump 38 from any suitable supply of tar or oil -to be distilled. Oil or ammonia liquor or other aqueous cooling agent can, When desired, be introduced similarly for the purpose of regulating the temperature ofthe gases. The gases may be precooled by thel introduction of oil or ammonia liquor through spry nozzles 39 supplied through a pipe 40 from any suitable source thereof. Y

In order to obtain maximum distillation at a high temperature, the uptake pipes and pre-cipltator can be best insulated by provid ing heavy insulation, or heating jackets, to prevent cooling of the gases from the ovens or retorts, so that the gases will pass through the precipitator at a high temperature, and so that effective distillation at a high temperature can be obtained.

The tar or oil to be distilled is introduced to the hot gases in finely divided formand, being mingled intimately Withthe gases, is subjected to the heat, thereof so that the desired volatile constituents are separated in the form of vapor. The gases carrying the vapor and some of the tar in the form of globules or tar fog, together With solid materials such as carbon, etc., in finely divided form, enter the tubes of the electrical precipitator and pass therethrough, being subjected to the electrical discharge whichthrough ionization of the solid and liquid particles causes them to separate from the gases and accompanying condensable vapors. The separated liquids, together with the solid par ticles, run down the inner walls of the tubes and are returned for furthervcontact with the hotl gases to the chamber at the bottom of the precipitator. Owing to the fact that the pitch in finely divided form which enters the tubes of the precipitator is liquid at the temperature of treatment, the latter are thoroughly iushed with relatively liquid constituents and accumulation of solid pitch thereon is avoided. This is the case with pitches produced from coke oven tar up to about SOO-325 F. melting point. At higher gas temperatures, with corresponding higher melting point pitches, accumulations of pitchy material may form on `the surfaces of the electrical precipitator tubes. The melting point range mentioned is not to be regarded as narrowly limiting, since conditions at different plants and with different tars will cause variations in the maximum permissible temperatures at each.` The pitch which is produced by the distillation can be withdrawn through an outlet 4l at the bottom of the precipitator and delivered through a pipe 42 to a pitch receptacle 43 from which it may be taken as required for any desired use. All or a portion of the pitch can be recirculated through a pump 44 and pipe 45 to the spray nozzles so that it will be again atomized and subjected to the heat of the hot coke-oven gases for further distillation and separation of vaporizable constituents therefrom, or the pitch may be recirculated directly from the bottom of the precipitator and the required amount may be continuously withdrawn to 43.

lllhe gases carrying the condensable vapors escape through an outlet 46 and are delivered through a pipe 47 to the condensing system. This may comprise a plurality of fractional condensers 48 in which the gases are cooled in stages to separate the desired condensable oils in fractions. The oils thus separated may be delivered through pipes 49 to receptacles 50 therefor. The gases, after cooling,

- may be conveyed by eXhauster 5l through a pipe 51 to the collector main or through a pipe 52 to the exhauster 23. In either case lthe gases freed from the condensable constituents are mingled with the gases derived from other ovens of the battery and are subsequently subjected to further treatment for the recovery of light oils, ammonia, etc.

In place of or as an adjunct to the spray nozzles, the electrical precipitator may be provided as indicated in Fig. 3 with mechanical spraying devices such as a cylinder 53 so disposed within the chamber at thebottom of the precipitator as to dip slightly into the tar or oil therein. The cylinder is adapted to be rotated at a relatively high rate so that the tar or oil in the bottom of the chamber will be thrown into the stream of gases in a finely divided condition and thus mingled thereyWith for the purpose of facilitating the distillation and separation of the oilconstituents. The cylinder may rotate, for example, at 900 revolutions per minute and when so operated will thoroughly atomize the tar or oil, returning portions thereof for further contact with the hot coke-oven gases to ensure thorough and effective distillation.

Referring to Figs. 4 and 5 of the drawings, the ovens of a cokeoven battery 55 may be connected by the usual uptake pipes and goose-necks 56 to a collector main 57 in which the gases may be cooled in the usual manner by the application of sprays of ammonia liquor or ammonia liquor and tar. The gases pass through a cross-over main 58 to condensers 59 wherein they are further cooled to separate tarry oil constituents. The tar which separates in the collector main 57 and cross-over main 58 may beA Withdrawn,-

through a pipe 60 and delivered to a decanter 6l in which the ammonia liquor is separated therefrom. The tarry oils which separate in the condensers 59 are delivered through a pipe 62 to a decanter 63 for the separation of ammonia liquor therefrom. The ammonia. liquor .passes through pipes 64 to a storage tank 65 from which it may be returned to a pipe 66 and pump 67 for further use in the collector' main. The tar from the decanters'l and 63 may be delivered to a storage tank 68 by pipes 69 or may be kept separate by providing tank 68. The gases from the condensers 59 are withdrawn through a. pipe 7 0 by an eXhauster 7l which maintains the pressure balance in the system. The gases may be treated subsequently in apparatus (not shown) for the recovery of ammonia and light oils in accordance with the usual practice.

To permit operation in the manner hereinbefore described a short collector main 7 2 may be provided preferably at the rear of th-e ovens and divided by diaphragms 7 3 into a plurality of distillation sections, each of which communicates directly with an electrical precipitator 74 of the type hereinbefore described. Eachof the distillation sections of the collector main is. connected to one or more ovens of the-battery through uptake pipes and goose-necks 75so that hot gases from the ovens may be delivered directly to the separate sections. The usual valves will be provided to prevent discharge of the hot gases from the selected ovens to the collector main'57 while distillation is in progress.

The tar or tarry oil to be distilled is introduced at one end of the collector main 72 `by a pipe 76 from the storage tank 68 or 68. Tar or oil from any other source such as aY storage tank 77 may be introduced similarly '30, of the precpitator into the respective disto the collector main, a pump 78 being provided to permit the introduction of the materials under pressure when required. The tar or pitch flows through the collector main past the diaphragms 7 3 which divide the collector main into separate distillation seo tions, and the resulting pitch is withdrawn through a pipe 79 and is delivered to a suitable storage `receptacle 80. In each of the distillation sections the material being distilled is intimately mingled with thev hot gases, for example, by a cylinder 81 rotating therein at high speed and dip ing slightly into the body of material in the ottom of the collector main. More than one such cylinder may be employed in each section if desired. Thus', in each section of the collector main the liquid material therein is subjected repeatedly to intimate contact with the hot gases entering the respective sections and the desired vaporizable constituents of the tar are thus separated therefrom and are carried with the gases into theelectrical precipitators 74.

In the electrical precipitators the gases are subjected to the electrical discharge which effects the separation of the solid and liquid particles in the gases, leaving the latter free from tarry constituents. The liquid and solid particles drain backwardly from the tubes tillation sections of the collector main. The precipitators will be operated at temperatures adapted to retain the desired oil constituents in the gases.

'lhe clean ,gases are' withdrawn through pipes 82 and are delivered to condensers 83 wherein they are cooled to recover the dcsired oils therefrom. The oils are withdrawn and are delivered to storage receptacles 84. Under proper conditions of operation these oils will vary in character as the result of the successive distillations of the tar and pitch A in the collector main. The gases from the condensers are delivered through pipes 85 and 86 and may be returned to the collector main 57 through exhauster 89 and pipe 87 or through a pipe 88 to the exhauster 71.

As in the preceding embodiment of the invention, the conditions of temperature in the collector main and the connected precipitators may be regulated by the addition of oils or ammonia liquorl with the tar to be distilled either separately 'or by mingling th oil or ammonia liquor with the tar before distillation, where a temperature lower than `maximum is desired. The invention can be utilized for the distillation of dirty oils either with or without the addition of tar thereto forthe purpose of recovering clean oils and particularly oils having different characteristics and being adapted therefore for different uses.

In some cases a limited distillation only of the tar is desired, and this can readily be gas at a high temperature, avoiding preliminary cooling of the gas, or by using alarger -amount of gas at a lower temperature, or by limiting its distillation by the use of ammonia liquor or added oil in regulated amounts.

In other cases, however, it is desirable to secure the maximum oil yield from the tar and the production ofhigh melting point pitch as a residue. This can readily be accomplished by insulating the uptake pipes. distillation main and precipitator, so as tu use the gases at practically their maximum temperature for the distillation and by regulating the supply of tar and the intimacy of spraying to obtain the desired distillation. Pitches of, e. g., 4000 F. melting point or higher and oil yields around 75 to 80% or higher are thus obtainable from coke oven tar.

The apparatus as described permits the distillationvof tar and oils andthe utilization for this purpose of a portion of the heat in the coke-oven gases, or of the heat of a portion of the gases. It likewise permits the separation of tarry constituents and solid materials from the hot gases and, when the operation is properly regulated, the gases passing to the condensers are cleaned and the oils separated therein are likewise clean and free from tarry constituents.

The advantages of the invention have been set forth and the preferred embodiments `have been described. It is to be understood, however, that various changes may be made in the lform and arrangement of the apparatus and inthe operation as described withoutdeparting from the invention or sacrificing -any of the advantages thereof.

While the invention is described more particularly as applied to coke oven operation, it is of broader application, and applicable, for example, to as retort plants for the distillation of tar y the gas retort gases. By insulating the uptake pipes or standpipes to reduce heat losses, effective distillation can be obtained with gases at a high temperature, while without such insulation, and with cousiderable atmospheric cooling of the gases, the distillation will take place with gases of lower temperature.

I claim:

1. The methodof distilling .tar and cleaning the resulting gases and vapors which comprises spraying tar into hot gases thereby dis4 tilling volatile constituents from the tar and loading the gases with finely divided particles of tar, immediately subjecting the resulting gases and vapors containing such finely divided particles of tar in suspension to an electrical discharge in an electrical precipitator whereby suspended liquid particles are precipitated onto the walls of the precipitator, and so regulating/,the distribution of tar in the gases that a continuous and voluminous obtained byusing a limited amount of hotow of precipitated liquid is produced on the walls of the precipitator thereby fiushing the walls and preventing accumulation of solid tar or pitch thereon. c

2. The method of distilling tar and cleaning the resulting gases and vapors, which comprises spraying lthe tar into a stream of hot gases thereby distilling volatile constituents from the tar and loading the gases with linely divided particles o tar, immediately passing the resulting gases and vapors containing such finely divided particles of tar in suspension in an upward direct-ion directly into and through an electrical precipitator 1ocated above the zone of distilllation and subjecting the gases and vapors to an electrical discharge therein whereby suspended liquid particles are precipitated onto the walls of the precipitator, so regulating the distribution of tar in the gases that a continuous and voluminous flow of precipitated liquid is produced on the walls of the precipitator thereby flushing the walls and preventing accumulation of solid tar or pitch on the walls, returning the precipitated matter directly to the still,

' blending it with tar therein, and continuing the distillation of the tar until it is distilled to pitch of the desired melting point.

3. ln the operation of a coal distillation plant involving a tar still wherein tar is distilled in contact with hot coal distillation gases, and an electrical precipitator wherein solid and liquid particles are removed from the gases and vapors resulting from such distillation, the method which comprises loading the hot gases with finely divided particles of the tar, immediately thereafter, while the gases are still at a high temperature and et contain a large proportion of tar partie es, subjecting the gases to electrical precipitation to precipitate residual liquid particles, the distribution of the tar in the gases being so regulated with regard to the volume and temperature of the gases that a continuous and voluminous iiow of the'precipitated liquid is produced on the Walls of the electrical precipi'tator thereby flushing the walls and preventing the accumulation of solid tar or pitch thereon.

ln testimony whereof I aix my signature.

STUART PARMELEE MILLER. 

